Pokemon GO special attacks and blue energy bars [duplicate]

Essentially these dictate how long until you can use a special attack - the smaller bars fill up faster, and you can store multiple charges.

But it should be noted that the bars doesn't affect the move's Damage Per Second though - they each deal a certain amount of damage over a certain time when activated. A more meaningful way of comparing each move is to compare their DPS.

For example with Poliwrath's special moves, Ice Punch does 13.5 dps while Hydro Pump does 20.7 dps (which is clearly superior).

But on this pokemon, to deal the most damage you should just use the Mud Shot quick attack, which does 21.8 dps - greater than any of the main moves. (The only exception would be when fighting against a pokemon type that is super Effective / Ineffective to your move type).

There is a general best moveset for each pokemon. You can find the whole list here. Obviously different movesets are optimized for different matchups but in general you should focus on getting the moves they list in the link.

Personally I like having either 2 or 3 bars. 4 bars fill up too fast and the animation takes a while so you might actually lose damage since your fast attacks might do more damage in the same amount of time. One bar takes too long to fill up and your pokemon might actually die before it can use it in a poor matchup and even then you are almost only able to use it once.