The Irish language is a Celtic language and is related to English only through their common Indo-European roots, which is quite far back. So, it is actually very different from English, more so than almost all other European languages.
If you know nothing of Irish, and would like to have a technical overview of how it works, you should take a look at the following link (a PDF file), which is hosted on the RTÉ (national radio and television service of Ireland) website www.rte.ie. It was prepared by Eithne Ní Ghallchobhair.
Some websites, documents and applications that exclusively concern the Irish language are mentioned and examined in the links to the left.
If you want to learn Irish on-line, there are several sites that might be of interest to you. There is further information about courses at the following link: Irish On-line Courses.