Google is your friend..
Improvements over 68010
The 68020 added many improvements to the 68010 including a 32-bit arithmetic logic unit (ALU), external data bus and address bus, and new instructions and addressing modes. The 68020 (and 68030) had a proper three-stage pipeline. Though 68010 had a "loop mode", which sped loops through what was effectively a tiny instruction cache, it had only two memory location and was thus little used. The 68020 replaced this with a proper instruction cache of 256 bytes, the first 68k series processor to feature true onboard cache memory.
The previous 68000 and 68010 processors could only access word (16 bit) and longword (32 bit) data if it were word-aligned (located at an address that is evenly divisible by 2). The 68020 had no alignment restrictions on data access. However, unaligned longword accesses were often much slower than aligned accesses.