Characterisation is the name given to any way in which the writer helps the reader to see what a particular character is like. It is achieved in a number of different ways. For example, an author might simply engage in direct characterisation where they tell the reader what a character is like. It might be more indirect, where a character is developed through what the character says and does. It can also be revealed through what others say and think about a certain character, to list a few.
Clearly there are many examples of characterisation in Phase 5 of this powerful novel, and just looking at the first chapter in Phase 5, Chapter 35, which is where Tess reveals to Angel about her rape, note how the following excerpt helps the reader to understand the characters of Tess and Angel more clearly:
These and other of his words were nothing but the perfunctory babble of the surface while the depths remained paralyzed. He turned away, and bent over a chair. Tess followed him to the middle of the room where he was, and stood there staring at him with eyes that did not weep. Presently she slid down upon her knees beside his foot, and from this position she crouched in a heap.
The way that his "depths" are described as being "paralysed" strongly suggests the way in which his notions of purity will become a barrier in his relationship with Tess because of this new knowledge. The distance that suddenly rises up between them becomes more tangible as he physically moves away from her, "turning away." Tess's actions in "sliding down" into a kneeling position as his feet shows the power relationship between them and her desperate fear of being rejected by the man she loves because of something she had little control over when she was younger. It is clear that this is an excellent example of characterisation, as it helps us to understand both Tess and Angel better, and also the relationship between them.