A. People

Collective nouns are used to describe a group of the same people or things.

B. Words associated with certain animals

A flock of sheep or birds, e.g. geese/pigeons; a herd of cows, deer, goats; a shoal of fish (or any particular fish, e.g. a shoal of herring/mackerel - note the use of singular here); a swarm /swɔːm/ of insects (typically flying ones, e.g. a swarm of bees/gnats).

A pack of ... can be used for dogs, hyenas, wolves, etc. as well as for (playing) cards.

C. People involved in the same job/activity

These nouns are used with singular or plural verbs, depending on your point of view.

• A team of reporters/rescue workers was/were at the scene of the disaster.
• The crew was/were saved when the ship sank. [workers on a ship/ambulance/plane]
• The company is/are rehearsing a new production. [group of actors]
• The cast is/are all amateurs. [actors in a film or theatre production]
• The public has/have a right to know the truth. [the people as a whole]
• The staff are on strike. (normally used with a plural verb; general word for groups who share a place of work, e.g. teachers in a school, people in an office)

D. Physical features of landscapes

In the picture we can see a row of cottages near a clump of trees with a range of hills in the background. Out on the lake there is a small group of islands.

E. Things in general

• a pair of birds sitting on a branch [two of anything that are the same]
• a couple of strawberries [vague way of saying two, not necessarily exactly the same]
• a pile/heap of papers (or clothes, dishes, toys, etc.)
• a bunch of flowers (or grapes, bananas, etc.)
• a stack of chairs (or tables, boxes, logs, etc.)
• a set of tools (or pots and pans, dishes, etc.)