Pick and Ban is a custom gamemode option introduced in Tom Clancy's Rainbow Six Siege in the Operation Para Bellum expansion. Available in the Ranked and Unranked playlists, it allows each team to ban one Attacking Operator and one Defending Operator for the entire match.
At the beginning of a ranked game, you and your team will have 30 seconds to choose an operator to ban. This means that a single operator won't be playable the whole game. You can pick whoever you want to ban, but its a team discussion. The operator that will be banned depends on the number of votes the operator has recieved. Since you 5 people on your team you have 5 votes, with the operator with the majority of votes being banned. The ban phase is also very important as you might find yourself playing ranked and your team decided to ban Jackal, Echo, while the other team banned Montage and Lesion, so you and others won't be able to play those operators the whole game, so you have to find another way around it, such as using Kapkan for area denial instead of Lesion.
For each round, after finishing picking the spawn point, the Operators and their loadouts, both teams are shown the Operator picks of the other team. At this point, both teams are given 30 seconds to either change their loadouts or to swap one of their Operators for a sixth choice.
The sixth choice is not shown to the other team.