Trello is, as said already, just a electronic board where you can create columns with work item in it. It doesn't (to my knowledge) contain a function for managing WIP limits (limit the number of items in a column). That function would be essential in any tool that is aimed against kanban usage. I don't Trello say they are either...
But it doesn't hinder you from using it as your board. You might make up other ways to limit WIP. Limit the number of items that are allowed to enter the board for example.
Hope this helps