I think you are referring to when a cat is in heat? This only happens to female cats, and basicly it means they have reached sexual maturity and the only thing on their mind is mating. It usually occurs every two weeks or so for about two days at a time. If it is allowed to occur more than a few times without her mating it can lead to serious health issues so it is best to get her spayed.
Male cats who reach sexual maturity will spray, this means they will urinate on just about anything, and its VERY stinky. To prevent this he needs to be neutered before he starts spraying because it is possible he will continue to spray even after he has been neutered if he has already started doing so.
If the cost of neutering is an issue there are many low cost spay/neuter programs out there, try doing a google search for them in your area. This should be done before the cat reaches six months of age.
As far as the cats in the area, unless you live in a very rural area (and even then unfortunately) it is best to keep your cat indoors. There are many dangers in the outside world for a cat, fleas, ticks, cars 8O , other cats, dogs, viruses, diseases, mean people ....etc.