Step 1: Start from the basic idea of federalism.
Federalism works by splitting government authority between a central government and state governments, with neither one fully in charge of the other.
Step 2: First feature, division of powers.
The Constitution lists out exactly which subjects belong to the Union, which belong to the states, and which are shared, through the Union, State and Concurrent Lists, so each level knows its own job.
Step 3: Second feature, the Constitution stays supreme.
Neither the Centre nor a state can act outside what the Constitution allows, and courts can strike down any law that oversteps this, which keeps both levels in check.
Step 4: Final answer.
So the two features are the constitutional division of powers between Centre and states, and the supremacy of the Constitution over both levels of government.