Is a DER encoded ECDSA signature. I'll break it down:
indicates that a compound structure follows (ECDSA signatures are treated as a compound of 2 integers, r and s)
is the total length of the compound structure (excluding the 2 header bytes, 30 45), 69.
the start of the contents of the compound structure, 02 indicates an integer (the signature's r value)
of 33 bytes
the integer's value encoded in 33 big-endian bytes. The first byte is zero, as without it, it would be interpreted as a negative number (see 2's complement notation).
another integer follows (s)
of 32 bytes
the 32 bytes encoding the s value
this is a sighash byte appended by Bitcoin, and is not technically part of the ECDSA signature. As such, it's not counted as part of the length 69 (byte 45) at the start. It indicates what fields of the transaction are signed. 01 means "all".