Learn French: Je préfère ce marché.

Ce is the demonstrative adjective (meaning "this" or "that") for masculine singular nouns. We use it here because marché is masculine and starts with a consonant. If it were feminine, we would use cette, and if it were a masculine noun starting with a vowel sound, we would use cet.

Does ce mean "this" or "that"?

It can mean either! French doesn't strictly separate "this" and "that" the way English does. Ce marché can translate to "this market" or "that market" depending on the context.

Why does the accent change in préfère compared to the infinitive préférer?

This is a spelling change to match pronunciation. The verb préférer (to prefer) has an "ay" sound for both accents. But for forms where the ending is silent (like with je, tu, il/elle, and ils/elles), the second accent changes to è (a grave accent) to make an "eh" sound: je préfère.

Are all nouns ending in -é masculine like marché?