Hello! I have site, in google it is example.com/, but I bought link and put www.example.com or example.com without /, it is important ?
No. This was discussed a week or so ago. Assuming you are on an Apache server, the trailing slash signifies a directory. Lacking the trailing slash, the server will, in almost all cases, first try to locate a file with that name, and failing to find one throw an error (check your logs) and resolve to the url with the trailing slash.
(as a continuation of what willybfriendly said) And therefor Google treats it as the same page with or without the slash so there isn't any penalty.
The problem arises when you have site1.com/folder1/ and site1.com/folder as you build links to subpages you will notice that google will treat them as different pages.