M2: why does it include M-Mkt MF's

Can someone explain to me why Money market mutual funds are included in M2. In terms of the Level 1 syllabus this is in Reading 24. -J

They’re very similar to a savings account. They earn interest, cannot be used to make purchases, but are readily redeemable into cash.

Thanks Marti. There is still some illiquidity in their conversion to cash and fluctuation in their values. Anyway, I will try to read more on this.