ShiftRows

During this process, the bytes of each row of the matrix with which the AES algorith operates (state) are rotated in a clycic way. It is a simple but necessary operation in which the bytes of the rows are rotated as follows:
The first row is not rotated, it remains unaltered.
Each byte of the second row is rotated one position to the left.
In the third row, the bytes are rotated two positions to the left.
And finally, each byte of the fourth and last row is rotated three positions to the left.

Thanks to this transformation, the resulting matrix contains the same bytes as the original matrix, which will be necessary for other parts of the whole AES process.
This process can be clearly seen on the following image: