Learn Russian: Мы любим мороженое.

Любим is the 'we' (first-person plural) form of the verb любить (to love). Because любить is a Type II verb (ending in -ить), it takes the -им ending for мы, rather than the -ем ending used by Type I verbs.

Is мороженое in the accusative case here?

Yes! Since it is the direct object of the verb (the thing being loved), it is in the accusative case. However, because мороженое is an inanimate neuter noun, its accusative form looks exactly the same as its nominative (dictionary) form.

Why does мороженое end in -ое instead of a standard neuter noun ending like -о or -е?

Мороженое actually comes from an adjective meaning 'frozen.' Over time, it started being used as a noun to mean 'ice cream.' Because of this, it keeps the neuter adjective ending -ое and follows adjective rules when it changes form.

Since this lesson is about plurals, how do you make мороженое plural?

Just like in English, 'ice cream' is usually an uncountable concept in Russian, so it stays singular. If you do need to say 'ice creams' (meaning separate servings), it becomes мороженые. Notice it takes a plural adjective ending (-ые) rather than the regular noun endings (-ы, -и, -а, or -я) you are learning in this lesson, because it still behaves like an adjective!