Your combat level is something by which you are known and respected for. If your's only level 5, then no one will respect you and everyone will call you a "noob", even if you have 80 woodcutting or 90 runecrafting. So it is important to train combat. Training combat in Runescape is not very hard if you know the proper locations. A good place to combat would be where there are not many people, the monsters don't do much damage, they have good drops and most importantly the place is not a multi-combat area. A multi-combat area is where many people can fight the same monster so other stronger people can attack your monster and steal your experience and possibly your drop. Here are some good places I found where you can train combat.
Moss Giants at Crandor
There are a few requirements before you can fight these. You must have done the dragon slayer quest so that you can go to the island of crandor. Crandor has lots of monsters to fight but the only interesting ones are the lesser demons and the moss giants. Only high levels can train on lesser demons so you should avoid them. The reason you should train here is that this place is mostly empty so you are free to fight as much as you want. The Moss giants drop big bones so you can also train your prayer. They also drop very good things like steel bars, black square shields and mithril swords. Not recommended for low levels.
Cockroaches
Near Edgeville, at the stronghold of player safety you can fight Cockroach drones (lvl 8-9), Cockroach workers (lvl 53) and cockroach soldiers (lvl 84). Players of all levels can train here. The best thing about these cockroaches is that they have very good drops. Fight them yourself to find out. Also, the cockroach soldiers hace a rare chance to drop a rune square shield which sells for 22k and is the best monster drop for free players.
Dark Wizards Outside Varrock
Near Varrock southern entrance is a stone circle surrounded by dark wizards (lvl 7 and lvl 20). Don't be fooled by their low levels as they can do some decent damage to even high level players. This is a very good place to train your ranging level. The wizards drop a wide variety of runes including Chaos, Nature and Law runes. Food is recommended.
Edgeville Guards
Kill edgeville guards is a great way for low levelled players to train their melee combat. The guards don't do much damage but food is stil recommended for people with low defence. There are no drops worth mentioning here but they are still a good way to level up and get stronger for better monsters.
Cows at Gnomecopters
North of lumbridge are the gnomecopters. There is a bank deposit box here which is very near to the Cows. You can kill Cows and deposit their cowhides and bones in the bank and then sell them later at the grand exchange. Not a very good place to level but a great place to make money and get combat experience at the same time.
Combat level doesn't say anything.
I'm level 63 atm, but I have 50 att - 70 str - 72 hp - 81 range - 70 mage and 44 pray.
It doesn't matter if anyone calls you noob, just ignore them