"I would like wine and bread."
Translation:Vinum et panem velim.
Welcome to the Subjunctive, the form of verbs that deal with hypothetical situations, reported events and anything that is not Indicative (i.e. actually happening). English often uses "would" or "may" to indicate the subjunctive, but we still have it in the form of things like "They suggest that he ask for it" (instead of 'asks'), or "We heard that he were detained" (instead of 'was'), or "Many believe that he be missing" (instead of 'is').
In Latin this has many additional uses, such as "let us...", e.g. vivere = to live, vivimus = 'we live,' but vivamus (note the vowel change) = 'may we live' or 'let us live!' In the above example, it softens volo (I want/wish) to velim (I would like).
Remember that the -m ending, like 'sum' (subjunctive 'sim') is cognate with English 'am', from Indo-European hésmi (Proto-Italic ezom > sum).
I get that these nouns are used in the Accusative case (because, etc) so thank you.
When these words are introduced as New Vocabulary in the Tips, I'm confused why they are presented like this:
Why vinum (Acc) and Panis (??? Case)?
To add to Moopish's answer, "multi" has different endings from what you usually see because, as the entry mentions, it's plural.
I'm not quite sure why Duo chose to list just the plural forms, because it can also be used in the singular to mean "much / a lot of": "multum vinum" = "a lot of wine." And so the forms you mentioned, "multi/multae/multa," are the plural forms of "multus/multa/multum" respectively, which match the usual pattern.