Can i use the images from this website ?

The images/media which are marked with the Public Domain license or those that can be downloaded without restrictions have been released to public domain by their authors or are ineligible for copyright protection. You can download, copy, modify, distribute and use the images / media files, even for commercial purposes. You don't have to ask for permission and you're not required to attribute the images (however this is welcomed). Beware that in some cases depicted content could still be protected by trademarks, publicity or privacy rights.

What leeftail means ?

Leeftail means "high in demand". You can read more about the meaning of the word here