What's the difference between the 'field' and 'field.keyword' fields in Kibana?

Question

When adding a filter in kibana all string fields have a entry and .keyword entry. What is the difference?

Answer 1

to add on to this in case it helps someone is that the .keyword field can be used to create scripted fields on the index if you already have a matching keyword field. Do not need to go through the trouble of switching fielddata to true and reindexing