Bronn describes the unique profession and skill of the Sellsword, as well as the debatable merits of the hedge knight.
Bronn:"Sellsword". Pretty much sums it up. A poor man has a sword. A rich man needs a man with a sword. Gold is exchanged. If the poor man knows how the use the sword, maybe he becomes a rich man, one way... or another. I'm sure sellswords have a long and illustrious history, but if you meet a sellsword who knows it, best hire someone else. A sellsword should be good at one thing: getting paid to kill people. It's not an easy job; most people try to kill you back, and at least a few of them know how. The ones that don't, well, they often come in enough pretty armor to ruin an afternoon.
A lot of high lords turn their noses up at sellswords. They say they can't trust a man who sells his allegiance to the highest bidder. I don't blame them; it's much cheaper for them to own an army from birth, either by people being on their lands or by their ancestors swearing a few oaths. But here's the thing: no sellsword has ever fled from the winning side. If your hired companies are running away from you, it's because you're not on that side - and you didn't pay them enough to die with you.
Not that you could. Sellswords don't get rich dying for their lords. Sellswords don't really get rich. Some of the eastern companies on Essos do fine: the Golden Company, the Second Sons, the Windblown. Always a bit of fighting to be had in the Free Cities, even if those merchant princes can be as tight as an old man's cunt. But then you're stuck in the heat and dust, hoping some dumb rich prick doesn't try to hire your company to fight Dothraki, because your dumb, greedy captain would probably take it.
Hedge knights, now, are a different breed. Take a sellsword and remove the sense. They get their name from where they sleep: under the hedges of the Seven Kingdoms and ditches and stables. They don't have the family name or the purse like real knights, so they spend all their money on armor, and a horse, and riding tourney after tourney in the hope of impressing some lord or winning some prize. One loss, and a lot of them are ruined. They can't ransom back their armor. Even if they win, think what a knight's good for: killing men. You know how you train for killing men? By trying to kill men, not prancing round with a blunted stick bowing and waiting your turn.
Maybe you think I'm just insulting the competition so you hire me instead. Well, of course I am. So don't hire me. Hire the sellsword with educated airs who tells you all about the great battles he's heard of, or the hedge knight who's won a few tourneys starting to build his name. And the man you're fighting against? He hires me.