Both are coatings applied to the interior of the goggle lens and are invisible to your sight. The Anti-Fog coating reduces the fogging experienced inside of goggles. The UV protection reduces a very significant amount of the UV A and B rays entering the goggle lens and protect your eye. Clear is the most popular color with smoke as second most popular color. Clear goggles provide excellent vision, especially in indoor pools where the lighting may be weak.
Smoke is a darkening effect and is good for outdoor swimming.
The other colors provide a varying amount of tint and differing aesthetic appeal. Everybody has different facial structures, and we all have differently shaped nose bridges, so most goggles have adjustable nose pieces. Goggles originally all came with a single rubber strap that goes across the back of your head to hold the goggle in place. However, this single strap sometimes moved up or down your head causing the goggle lenses to move. Many of the newer goggles have gone to split head straps, where there are multiple strap lengths across the back of your head.