Learn German: Ist der Wind gut, fährt das Segelboot schnell. - If the wind is good, the sailboat travels fast.

This is a conditional clause without wenn (if). By dropping the word wenn, the conjugated verb (Ist) moves to the very first position in the sentence. It means the exact same thing as a normal wenn sentence, but is often used in both spoken and written German for a faster, more concise rhythm.

Since it starts with a verb, how do I know it's an "if" statement and not a question?

The punctuation and the second clause give it away! A standard yes/no question would just be a single clause: Ist der Wind gut? (Is the wind good?). Here, the comma connects it to a second clause that also starts with a verb (fährt). When two verb-first clauses are glued together like this, it forms an "if [this], then [that]" structure.

Why does the second half of the sentence start with fährt instead of das Segelboot?

This happens because of the V2 rule (the rule that puts the conjugated verb in the second position of a main clause). The entire first clause (Ist der Wind gut) counts as "Position 1". Therefore, the verb fährt must come immediately after the comma to take "Position 2", pushing the subject (das Segelboot) into the third spot.

How would this exact sentence look if I decided to use wenn?