When you make black tea you'll normally categorise them i four sizes. Whole leaf, broken, fannings and dust. Whole leaf is like it sounds whole leafs, broken is leafs that i broken into 2 or 3 pieces. Dust is the smallest, which you'll normally find in teabags and fannings is a size in between Broken and dust (better teabags can have fannings in them for example.)
There's also CTC, which means crush tear curl, which is a production type of black tea that resolts in something that looks like small balls (see picture from USAGI-WRP with creative commons 3.0 licence)
Which size is your favorite?