What does EIT, MHW, Freesat, ViaSat etc EPG's do?

[anothernoob]

So now I got my box working as I want thanks to help from users here, I've switched 'no' to the following and it hasn't changed much from what I can see in the EPG (box has just completed it's daily update) so just wondering what they do and if it's better to leave them on or not:

Enable EIT Epg
Enable MHW epg
Enable Freesat Epg
Enable ViaSat epg
Enable Netmed epg
Enable Virgin epg

And what do the following do (I have these enabled still):

Enable EIT in http streams
Enable AIT in http streams

 

[FreeUK]

EIT is from Myth TV software, MHW = Media Highway EPG has been there since the start of the Dreambox receivers, Freesat 28 east, Viasat 4.8 east, Virgin = Cable, Netmed not sure

Enable EIT and AIT eit is for the EPG and AIT is for HBBTV use

 

[anothernoob]

Thanks. I'm using XMLTV EPG so can I leave those 6 EPGs off or will there be any conflicts?