What is meant by lanthanides and actinides?

What are lanthanides and actinides?

What is meant by Lanthanide contraction? Write the general electronic configuration of inner transition elements.

What are lanthanides and actinides? Where are they located in the long from of the periodic table?

Give three similarities between lanthanides and actinides.

The common oxidation sta te of lanthanides and actinides is-