Glossary
Timeout
In one line: A break in the match to talk and change the plan: in organized matches it is a real pause, in normal games it is a quick talk during the buy phase.
What it means
In tournaments and some modes, teams can call a tactical timeout: the game pauses for a while and the team talks. Normal matchmaking has no such pause, but the team can use the buy phase as a "mini timeout": a few seconds to say what is not working and what to do next round.
A good timeout gives one or two concrete points ("they always have two in mid, let's go B through main"), not a list of every mistake. It also helps break a losing streak and calm the team down.
An example
You lost four defense rounds in a row on A. During the buy phase your IGL says: "they always rush, let's molly main early and the third player stays A". One clear change for everyone.