They are two different dynasties from Morocco that ruled mostly the Maghreb and Iberia.

The Almoravid came from Berber tribes living in the desert in the south that conquered the different political groups in the country, including the previous dynasty, the Idrisid. The Almohad came after the Almoravid, from Berber tribes in the mountains that, again, reconquered the country.

Both dynasties started as reactionary movements to reform the religious and political aspect of the region. Each movement considered the previous political group as heretical and not hardline enough. They blamed the decentralization, political weakness and corruption on decadence and heresy: the previous dynasty lost its right to rule, it was time for a new family to unite the region.

Each dynasty unified the country, expended in the Maghreb and started intervening in Iberia by absorbing the Andalusian Taifas and fighting the Christian Kingdoms to reconquer recently-lost land. Both dynasties fell when their ruling dynasties got corrupt, slowly losing control of whatever people they subjugated and ruled over.

Later Moroccan dynasties rose up and reunited the country (see a pattern here?), this time with little-to-none Iberian possessions (Marinid, Wattasid, Saadi, Alaouite).