Can not understand the sequence length and hidden size of the BEiT model

🤗Transformers
1

The output shape of the last_hidden_state is [8, 197, 768]. As far as I know, the first is the batch size, the second is the sequence length and the last is the hidden size. But I am unclear about the sequence length and the hidden size. The code is given below:

with torch.no_grad():
    outputs = model(batch['pixel_values'])

print(outputs.last_hidden_state.shape)

torch.Size([8, 197, 768])

Can anyone explain what actually sequence length and hidden size mean? Thanks in advance.