Vamana means to induce vomiting, it is a bio-purification measure meant for the elimination of morbid doshas (mainly Kapha & Pitta) accumulated in the upper gastro-intestinal tract & respiratory tract (Amashaya and Kaphashaya)
Add the second shloka here As the flowers, fruits and branches are destroyed at once, as soon as the mother tree is rooted out; similarly the diseases originated due to vitiated Kapha dosha are subdued through bio-cleaning procedure of Vamana.
Though, Vamana is a completely independent bio cleansing procedure, generally it is preferred before Virechana (Therapeutic purgation) because if Virechana is administered without Vamana, the vitiated Kapha may descend to mask Grahani(duodenum) causing Agnimandya.