Briars are the original wild roses. Roses that you buy for your garden have been bred for colour/scent/disease resistance etc. Once a new rose has been created it can only be duplicated by taking cuttings from it. You can either let the cuttings grow roots, as you do with geraniums etc, but the usual process is to graft them on to a briar root. If you look at any roses you have you will see a lump in the stem around ground level; this is where the graft was made. Your rose, then, will have a briar root and a hybrid top; unfortunately the briar root sometimes throws up new shoots; these are called suckers and will not produce the sort of flowers that you want. If you do not remove suckers the briar will eventually take over the plant.