Horde refers to a large crowd, mob, gang, throng or swarm. It is always a noun and applies to people and other living beings and often has an aggressive connotation:

• Hordes of reporters followed the Duke and Duchess of Cambridge on their recent visit to NZ.
• The sheep were attacked by a horde of ravening wolves.

Hoard can be either a noun or a verb and is usually applied to things, often valuable things such as money, treasure or food.

The noun hoard refers to an accumulated store often hidden, or a supply of something that has been stored up and often hidden away

• In George Eliot’s story, Silas Marner, the main character becomes a miser who amasses a hoard of gold.
• Alcoholics tend to become expert at concealing their hoard of bottles.

The verb to hoard means to accumulate a store or cache, to collect and hide away or to keep something to oneself.

• After the war, it came to light that the Nazis had hoarded numerous works of art.
• When a haulage strike is threatened, people often start hoarding food in case supplies are affected.

Composite example:

• If you have a hoard of something, a horde of people might try to take it from you.