It is impossible to tell whether a material contains asbestos just by looking at it. This can only be confirmed by analysis of a sample in a laboratory. However, there are typical uses for it which will help in locating possible 'asbestos containing materials' (ACMs).
ACMs are more likely to be present in buildings constructed or refurbished before blue and brown asbestos were banned in 1985 and not in new buildings. They were particularly used in buildings built in or before the 1970s.