These days, it's all about HDMI, which is used to connect everything from set-top boxes to video streamers, Blu-ray players to games consoles. Thanks to ARC/eARC (Audio Return Channel / Enhanced Audio Return Channel), a single HDMI connection can even be used to output sound to an AV receiver or soundbar at the same time as it receives a video signal.
Currently, three HDMI connections is standard on budget and mid-range TVs, while four is the norm for premium models, including every OLED that we're aware of.
The specification of the HDMI connections tends to differ depending on the price of the TV, too, with premium models now commonly getting at least two HDMI 2.1 sockets. These have greater bandwidth than their HDMI 2.0 counterparts and can support advanced formats such as 4K@120Hz and 8K@60Hz. Fancy gaming features such as Auto Low Latency Mode and Variable Refresh Rate are often supported via HDMI 2.1 sockets, too, though not always. It's sensible to check the specs thoroughly if there are particular features you're after.
After HDMIs, USB ports are the most abundant on modern TVs. You can use these to keep devices charged (often particularly useful for stick- or dongle-style streamers), and some TVs allow the connection of flash drives and hard drives for the recording of live TV content.
On the subject of live TV, you can expect practically every TV to have an aerial socket via which it can receive Freeview broadcasts, but many also have a satellite connection. Be warned, though; the presence of a satellite connection doesn't guarantee that there's a Freesat tuner on board. Without one, you'll receive only a patchy and disorganised selection of satellite TV channels.
Other useful connections include optical and stereo outputs, which can be used in lieu of HDMI ARC to connect legacy audio equipment. Headphone outputs are still fairly common, too, although they're beginning to be phased out in favour of Bluetooth – a trend started by Samsung and now being followed by the likes of Sony.
Lastly, while some TVs feature composite inputs (often via an adapter), most – even at the budget end – have phased out legacy connections such as SCART. So those clinging on to old video cassette recorders, for example, should be aware of that.