This official guide, produced by the DVSA, contains all you need to know about traffic signs, signals, road markings and a whole lot more.
The guide above is a handy one but it is quite in-depth. If you just want a quick list of lots of road signs and their meanings then checkout the official government list.
If you like the detail then checkout Wikipedia which really gets into this subject.
Or watch below as they are all explained in brief.