Does a land with a basic land type count as a basic land for purposes of effects that say basic land?

A land being 'basic' is a supertype printed in the type line, not a consequence of having a basic land type. The Comprehensive Rules define basic lands as lands with the supertype 'Basic' (CR 305.6). Effects that refer to 'basic lands' look specifically for that supertype, not for the subtypes Plains, Island, Swamp, Mountain, or Forest.

Basic land types (Plains, Island, Swamp, Mountain, Forest, Waste) are subtypes that grant a mana ability (CR 305.6, 305.7). Any land — basic or not — can have these subtypes. For example, the card Stomping Ground has the subtypes Mountain and Forest, but it is not a basic land because it lacks the Basic supertype.

This distinction matters for effects like 'search your library for a basic land' or cards like Back to Basics (which affects nonbasic lands). A Stomping Ground would be found by 'search for a Mountain or Forest' but NOT by 'search for a basic land,' and it WOULD be affected by Back to Basics.

Concrete example: Your opponent controls Stomping Ground (a Mountain Forest). You cast Back to Basics, which taps all nonbasic lands. Stomping Ground taps and stays tapped — despite having basic land types, it is not a basic land and is fully affected.

To summarize the key distinction: Basic supertype = the land is 'basic.' Basic land type (Plains/Island/etc.) = the land has that subtype and its mana ability. These overlap on cards like Plains and Island, but they are separate characteristics per CR 205.4b and CR 305.6.