In order to be reading this post, I will assume you have already read section 1 (if not, it is highly recommended).
Once you understand all the laws, and are now looking into getting your own kit, it is useful to understand that (as in every aspect of retail) certain brands are of a superior quality to others. You also need more than just a gun to play. The phrase 'you get what you pay for' truly does apply in this industry, which is something everyone should keep in mind when getting into airsoft.
Most airsoft guns are powered by electric, spring or gas power. This means a battery, bolt action with a spring, or compressed gas propel a plastic ball bearing (BB) out of the barrel of your gun. I wouldn't worry about learning the insides of an airsoft gun until you are a bit more experienced with the basics.
For a beginner I would always recommend purchasing a G&G Combat machine. The reason for this is that they are cheap, and perform brilliantly. They are battery powered (which we will get into next), but the main thing to understand is that the G&G Combat machine are a brilliant line of guns, which every new player should consider getting. They're easy to use and don't require a great deal of maintenance.
Whilst there are cheap and cheerful brands out there that will do the job, you can usually rely on the fact that if you're more experienced and you pay more for a gun, you'll get more out of it. For example you can pick up a good G&G combat machine for under £150, but if you want the highest end of guns either the Systema or TM recoil, they will set you back anywhere between £500-£1000. This isn't including mags, batteries etc. So for a beginner its best to stick to G&G and then once you are more experienced its easier to convert over to higher end guns such as G&P or WE.