Languages can be grouped together in different ways. One can put languages together based on their family relation (e.g. Uralic languages, Indo-European languages) or the area where they are spoken. But maybe the most interesting and eye-opeing way of grouping them is by their morphology. As it turns out, there are only four morphological groups for languages and all spoken languages fall into one of them.
Isolating languages don't express anything grammatical in their morphology and usually they don't have too many morphemes at all. In layman terms, this means that the words of the language don't inflect. In English for example, we make a distinction between walk and walked, the past and the present, by adding an -ed morpheme at the end of the word. In a strongly isolating language, this would be expressed as two separate words, for example "walk yesterday" would be enough to reveal that we are dealing with the past tense. An example of such a language is Chinese.
Word order is usually very strict in these languages, because otherwise it would be impossible to distinguish for example a subject from an object. This is the case in English as well; "the dog ate the pizza" means a whole different thing than "the pizza ate the dog". 😂
Common examples of agglutinative languages are Finnish and Turkish. In these languages morphemes are added quite systematically to the end of words to express different grammatical meanings such as number or case. For example the word for dog is koira in Finnsh. If you want to say "also in my dog" in Finnsh you would do this by just adding endings to the word koira in an orderly manner: koirassanikin. Here -ssa means "in", -ni means "my" and -kin "also".
The endings we saw earlier are called suffixes. A morpheme that appears in front of the word is known as a prefix (e.g. irrelevant). A general word for these morphemes is affix. The list of affixes is longer than this, though. There are infixes that appear inside of a word such as jokin (something in Finnish) becomes jossakin (in something). Circumfixes appear around a word such as in Geman gesagt (said) from sagen (to say).
In some languages, the morphological border is not as clearly defined as in Finnsh. In such languages changes occur in multiple positions inside of a word in such a way that it becomes impossible to mark the borders. This phenomenon is observable in English in some irregular verbs such as eat and ate. There's no clear line between the word itself and the past tense. Arabic is one of these languages.
Out of all the morphological categories, I find the polysynthetic the most interesting one. In these languages one sentence can easily be one word. Yup, you read right, a word equals an entire sentence! 😮In an eskimo language the word angyarpaliyugngayugnarquqllu translates into "he can probably also make big ships".
This is the morphological division of world languages. Of course, the lines here are not clear cut. I myself would consider English an analytic language even though there is some inflection going on. In the case of English, it's just almost nonexistent. 😊