Generally, a ghillie suit is made up of colored strips of burlap. The strips are of different lengths, widths, and sometimes frayed at the ends to avoid creating hard edges. Colors can be anything from plain, original burlap (brown), to various tints like greens, tans, and other colors found in nature.
These strips are then threaded or sewn onto a garment which can be a one-piece or two piece outfit. The garment can be mesh-like or solid. Due to the amount of material in a ghillie suit, they can become quite warm (or hot) as it's like wearing a full-body coat.
Sometimes one may want to incorporate local vegetation like leaves, weeds, branches, etc. into the the ghillie suit (usually when on-site) to help blend in to the immediate environment.
Ghillie suits were first developed by game wardens in Scotland (or was it Ireland?) to conceal themselves from poachers. Ghillie suits are, today, popular amongst some hunters - but are most commonly seen (or unseen - LOL) on military snipers in the field.....local conditions (climate, vegetation, etc. etc.) permitting. A sniper may spend days, even weeks, perfecting his own, custom, suit.
Ghillie suits are also sometimes seen in photos and videos - whether by chance, or on purpose - and mistaken for BFs.