Error message in image upload

[eluser]Rubiz'[/eluser]
Hello all.

I have a image uploader in my web site, but when I try to upload big images, size and kbytes, it returns me an error message, like this:

Allowed memory size of 25165824 bytes exhausted (tried to allocate 10304 bytes) in /hsphere/local/home/sergiopo/sergioporto.com.br/admin/system/libraries/Image_lib.php on line 1157

Anyone could tell me what does it means?