There are different types of abortion depending on which stage the pregnancy is at.
If the pregnancy is at an early stage you can take a pill which kills the feotus and flushes all the remains out of your womb. This can be quite painful and emotionally upsetting as you actually see the remains in the toilet.
Up to around 13 weeks pregnant you can have what is called a D&C.
A tablet is inserted into the vagina to loosen the neck of the womb, you are then put under aneasthetic and the surgeoun scrapes out what is in your womb. Obviously there are risks associated with it but it is pretty standard procedure (many misscarriage sufferers have the same op) and it usually goes without incident.
Side affects from abortion tend to be more emotional than physical. Many people have feelings of guilt and / or depression afterwards. This can last a few weeks or for years depending on the person. However some people dont experience any of this.
If you have an abortion councilling or support groups are usually offered if you need them.
The full long term emotional side effects of abortion are not known, probably because each individual reacts differently and the fact that it is a very private thing,
Much will depend on what your reasons for choosing abortion are.