Syntax is a concept that governs the structure of sentences. The order in which words are put together has a bearing on the meaning of a sentence as a whole. Syntax rules must be followed in order for a sentence to be grammatically correct and to make sense to speakers of a language. It is what dictates things such as the order of the subject and verb, and how adjectives and adverbs are used.
Morphology is the study of morphemes, which are the smallest unit of meaning in a language. A morpheme can be one whole word or a prefix or suffix that is understood to change the meaning of the word and therefore takes on meaning itself.