Test cricket
A standard Test is scheduled across five days with two innings available to each side.
ODI cricket
A standard ODI gives each side one innings of up to 50 overs.
T20 cricket
A standard T20 gives each side one innings of up to 20 overs. Interruptions and competition conditions can alter an individual match’s allocation.
Use the exact conditions
Read the actual competition instructions for exceptions, ties and interruptions. A format label is not a complete rulebook.
Official reference
https://www.icc-cricket.com/about/cricket/game-formats/the-three-formats