In your speaking test, the examiner will be marking you on for things: fluency and coherence, lexical resource, grammatical range and accuracy, and pronunciation. In each of those areas, you’ll get a band score from one – the lowest – to nine, the highest. The average of those four scores will be your final band score for the speaking paper.
Fluency and coherence
This describes how fluent and connected your English sounds. Do you speak without much hesitation and do you use a range of different way to connect your ideas?
Lexical resource
This describes how wide your vocabulary is. Can you talk accurately about any topic and use idiomatic language?
Grammatical range and accuracy
This describes both the range of different grammatical structures you can use and how well you use them.
Pronunciation
Can you be easily understood at all times?
Source: Future Learn - Understanding IELTS