How they form
Some kinds of rock are more resistant to erosion than others, and where bands of these different rocks are next to each other is where headlands and bays are formed.
1. Alternating 'bands' of less/more resistant rock are next to eachother along the coast line
2. Less resistant rock is eroded very quicky by the tide, forming a gentle slope.
3. The more resistant rock either side of this is eroded much more slowly, leaving headlands either side of the bay sticking out into the sea. They have very steep sides and often include features like caves and arches.