What do Pair, L, T stand for in the code?

Hi, I'm a beginner and would like to ask a question. What do Pair, L, T stand for in the code? What do they mean?
```
# Pair x L x T x 3 x H x W
video = np.zeros((len(s), self.max_frames, 1,
                  3, self.rawVideoExtractor.size, self.rawVideoExtractor.size), dtype=np.float)
```