Held

The character is 'frozen' motionless for the duration of the spell. They cannot move, attack, or use items. A playable character cannot be directly selected. They can receive items, but no items can be taken from their inventory. A creature Held is considered 'Helpless' by the game engine.
Being Held, or paralyzed is of a physical nature and therefore curable by Remove Paralysis. A Potion of Magic Blocking would also cure the effect, but since the affected subject is unable to administer the potion, it is not a viable treatment. Hold Creature is implemented with three Opcodes in the game, and they are very similar in function. The historical official name labels in the game IESDP Opcode library were as follows: 
State: Hold Creature I [109] (Current name: State: Paralyze) 
State: Hold Creature II [175] (Current name: State: Hold)
State: Hold Creature III [185] (Current name: State: Hold II)
Until recently, there is no status effect state actually named 'Paralyze, Paralysis or Paralyzed' in the game engine. There are various associated string references with those terms, depending on the source of the status effect. 
Some explanatory views of these Opcodes in the game, are laid out by the Sword Coast Strategem's developer and author David W. from the Gibberlings Three EE Fixpack Discussion, March 2022, which is posted below:
Being Held, or Paralyzed is typically implemented using three different Opcodes:
109: is used almost exclusively by items that cause paralysis, such as the undroppable weapons used by ghouls and carrion crawlers. The IDS check is rarely functional: you're affected by a 109 unless you have explicit protection from it. It is almost always associated with the 'Paralyzed' string. Many classes of monster - dragons and undead, for instance - are immune to it; you also get immunity to it from Free Action, Chaotic Commands, et al.
Complicating matters, though, 109 is *also* used by Web spells, both in BG1 and BG2 (the 'mimic glue' effect in BG2 also uses it). This is actually unnecessary, at least in EE: the web effect (opcode 157) is invariably associated with Web, and it imposes the paralyzation condition all by itself. However, it's clear that Bioware *didn't know that* and thought 157 was cosmetic (and they may have been right: I'm not sure whether this is EE behavior). There are quite a number of places in BG1 and BG2 where it is fairly clear that creatures are given 109 immunity because they are supposed to be unaffected by webs. (It's fairly clear for wyverns, which have no obvious lore reason not to be affected by paralysis (and are big enough to look stupid when Web Effect Overlay plays over them) and have an item that blocks 109, 157, and Entanglement effects; it's equally clear for Kuo-Toa, who get similar immunities to implement their PnP slipperiness trait; it's probably true for Beholders, who can presumably float above webs but have no obvious canon reason to get paralysis immunity.)
175: is used pretty much exclusively by paralyzing spells, almost always labelled 'Hold' (Tanar'ri paralysis is an exception) and is almost always associated with the 'Held' string. Creature immunity doesn't normally affect it: you get immunity to it through situational things like Free Action.
185: is used *very* rarely, and very few things are immune to it. In vanilla BG1, *nothing* is immune to it, and the *only* spell or item which uses it is Otiluke's Resilient Sphere. I think the underlying idea is that 185 represents things that physically prevent you from moving, but through some external barrier rather than directly slowing or freezing you. (On this basis, players should never be immune to 185, and probably only minhp1 items should grant it, to avoid the usual scripting problems. In BG2, however, I think the logic of this breaks down quite badly: boss monsters get immunity to 185, but it gets granted by some items/spells that really shouldn't grant it (some but not all fixed in FP or EE). I think the designers kind of lost track of what they'd intended. They also use 185 to double up as a cutscene can't-be-blocked effect (e.g. HELL_HOLD), but that is (or should be!) harmless since players shouldn't be protected from 185 anyway.
===Mod content===
The upcoming release of Enhanced Edition Fix Pack (EEFP) has already beta coded a large overhaul pertaining to Held, as follows:
Revamp of Hold, Paralysis, and Web 
In the original Baldur's Gate, there were four internal methods to make an NPC freeze: paralysis (used in undead melee attacks), web (used by the spell of the same name and spiders), and two forms of hold (one for Hold spells and a second, special one reserved for special cases like cutscenes).
As the series progressed through the BG expansion, into BG2, and concluding with Throne of Bhaal, these were used more and more freely, and muddled--you had web spells using paralysis, abilities that blocked the special hold (which nothing should) to the point where there was little distinction, if any, between these effects from a player's point of view. 
EEFP is re-establishing the scheme, going all the way back to the original Baldur's Gate, of trying to use these effects in a way that differentiates them and fixes a number of bugs along the way. Paralysis is, once again, the domain of undead attacks, and from which elves have some protection. Web is no longer paired by default with paralysis, meaning items which protect you from web no longer provide paralysis protection by accident, and the special hold will now always take effect.