While it's unlikely anyone's ever going to test you on the names for the various parts of a paint brush, they do exist ... so here they are in case you're ever in an art trivia quiz contest.
The handle of a brush is most often made from wood that's painted and/or varnished, but it can also be made from plastic or bamboo. The length is variable, from really short (such as those in a travel paint boxes) to really long (ideal for big canvases). What's more important than length is that the brush feels balanced in your hand. You're going to be using it a lot, so it needs to be comfortable to hold.
What bristles or hairs are in a brush is also variable, depending on what the brush is intended for (see: Painting Brush Hairs and Bristles). What's important is that they're firmly held and aren't going to fall out constantly as you paint.
The ferrule is the part that holds the handle and hairs together, and in shape. It's usually made from metal, but not exclusively. Mop brushes, for instance, can have a ferrule made from plastic and wire. A decent-quality ferrule won't rust or come loose.
The toe of a brush is the very end of the bristles, while the heel is where the bristles go into the ferrule at the end the handle (not that you can usually see this without taking a brush apart). The belly is, as the name would suggest, the fattest part of a brush. (It's most obvious on a round brush, rather than a flat one.) A substantial belly on a round watercolor brush enables you to pick up a large quantity of paint at a time.
The handle of a brush is most often made from wood that's painted and/or varnished, but it can also be made from plastic or bamboo. The length is variable, from really short (such as those in a travel paint boxes) to really long (ideal for big canvases). What's more important than length is that the brush feels balanced in your hand. You're going to be using it a lot, so it needs to be comfortable to hold.
What bristles or hairs are in a brush is also variable, depending on what the brush is intended for (see: Painting Brush Hairs and Bristles). What's important is that they're firmly held and aren't going to fall out constantly as you paint.
The ferrule is the part that holds the handle and hairs together, and in shape. It's usually made from metal, but not exclusively. Mop brushes, for instance, can have a ferrule made from plastic and wire. A decent-quality ferrule won't rust or come loose.
The toe of a brush is the very end of the bristles, while the heel is where the bristles go into the ferrule at the end the handle (not that you can usually see this without taking a brush apart). The belly is, as the name would suggest, the fattest part of a brush. (It's most obvious on a round brush, rather than a flat one.) A substantial belly on a round watercolor brush enables you to pick up a large quantity of paint at a time.