Can you tell me what to do with the canister? Replace the entire thing?

Can somebody give me a primer on what the purge system actually does? Thanks.

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Thank You!
Fred
2009 ML350
2004 SL600
2004 SL500
1996 SL600
2002 SLK32
2005 CLK320 cabrio
2003 ML350
1997 C280 Sport