Here are some major changes since previous release (7.24) as in Drupal 7.25 release notes:
- Performance improvement: Prevented block rehashing from writing blocks to the database on every cache clear and cron run when the blocks have not changed. This fix results in an extra ‘saved’ key which is added and set to TRUE for each block returned by _block_rehash() that actually is saved to the database (data structure change).
- Fixed a bug which caused cached pages to sometimes be sent to the browser with incorrect compression. The fix adds a new ‘page_compressed’ key to the $cache->data array returned by drupal_page_get_cache() (minor data structure change).
- Fixed broken tests on PHP 5.5.
A good start is at Translating content argument at Drupal.org
All modules has to be downloaded and installed from the web interface or by uploading all in the yoursite.ext/public_html/sites/all/modules/ folder
Some dependencies (for example Locale or Content translations) has to be checked to enable all modules.
After it has to be enabled in the yoursite.ext/admin/structure/types all the type of contents that will be translated from the native language.
Best practice is to set at multilingual settings: