What do فرض عين (individual obligation) and فرض كفاية (collective obligation) mean?

Scholars divide the obligatory (wajib) into two categories: Wajib 'Ayni (individual obligation), which is what the Lawgiver has commanded every individual to perform, such as prayer; and Wajib Kifa'i (collective obligation), which is what the Lawgiver has commanded the Muslim community as a whole to perform. If a sufficient number of people undertake it, the obligation falls away from the rest; otherwise, all are sinful. Examples of this include jihad in the way of Allah, washing the deceased, praying over them, and burying them.