PKCS#1, prior to version 2.0, described a single encryption scheme. From version 2.0, the OAEP padding was added to PKCS#1, and the previous encryption scheme has been retroactively called "v1.5" (because that's the only scheme which was described in the 1.5 version of PKCS#1). In PKCS#1 itself, the two encryption schemes are called "RSAES-OAEP" and "RSAES-PKCS1-V1_5".
The OAEP padding can theoretically be used with many other asymmetric encryption schemes, but RSA is (by far) the most widely used asymmetric encryption system.
Coloquially, RSA encryption with OAEP padding is often known as "PKCS#1 v2.0 encryption" since the older scheme is called "PKCS#1 v1.5 encryption", but this is not an "official" name. Both OAEP and v1.5 are standard and supported by the recent versions of PKCS#1, so v1.5 is no less a "v2.0" scheme than OAEP. As I said above, the official name (as defined in PKCS#1) is "RSAES-OAEP".