When I use antivirus ( AVG ) to remove virus, it says to either 'heal' or sometimes '

What is this Vault ?

Do it have some capacity ?

Is it safe ?

When I use antivirus ( AVG ) to remove virus, it says to either 'heal' or sometimes 'move to the Vault'.......antivirus scan

The vault isolates the virus so it cannot harm your system. You can then attempt ridding your computer of the virus using AVG. If this fails, a Google search of the virus name should give you links to a site where you can download a patch to solve the problem.

When I use antivirus ( AVG ) to remove virus, it says to either 'heal' or sometimes 'move to the Vault'.......computer security

Cleaning is where the software can remove the vrus from the file.

Vault is a secure location where the virus cannot infect the rest of your system from. This is in case there is some critical application or information which is so valuable you would risk infection to access it. In a few cases software can be used to remove the virus from the file, but most of the time you have to delete these.

First, try to clean, then move to vault and delete some time in the future after you have verified this is not critical.

Ido not think there is a specific limit - but after a couple of days you have verified your PC runs OK with the file in the vault and verify the file does not have critical personal info, there is no reason not to delete it.
press F1. Most programs use that shortcut to open their documentation. The best help always comes from their creators.