Language development is important at every kid and consists from several stages that evolve from simple to complex. Infants start without any formal language, and in the first months of their live they express themselves just thru gestures and simple sounds like crying or laughing, starting after to talk. Here are some approximate time frames for general language development milestones.
In the first month of its life, the infant will be able to express himself just by crying or making different sounds.
When he reached the age of 3 months he will be able in expressing himself also by laughing (that is more enjoyable than crying) and making different sounds like coo and goo. Also he starts to have different types of crying for different feelings like hunger or upset.
Between 4 and 6 months he will start to repeat simple sound combinations like da-da or ba-ba. In this moment you could say that the baby is talking in his own strange language. He also becomes able in communicating different type of demands through sounds or gestures.
When the kid is between 7 and 12 months old, more consonants will appear in his language, and he will even start in saying his first simple words like mama or dada.
When he reaches 2 years, he will already be able of having over 20-30 words in his vocabulary and saying different simple phrases made out of 2-3 words. For sure we will pronounce words clearer now. Once with his growing, more constants appear in his pronouncing, making the words clearer. The toddler will also understand simple commands tasks like: “come here”, “bring the bottle”. Also he will be able to understand simple questions like “Are you hungry?”, “where is the ball?”
At three years old he will already be capable in correctly pronouncing most words, and will start using phrases made out of 3-4 different words, and even using more than a subject and a verb. He will probably use adverbs and adjectives as well. His vocabulary will become bigger as each day passes by.
When the child is 4 years old, he should already start using without problems full sentences, and at 5 years speak fluently and clearly, using correct grammar. Also at this age he should be able of understanding full childrens stories and saying resumes based on what he understood.
Toddler language development is very important so if your kid has problems in reaching these specific milestones, you should seriously take in consideration consulting a specialist. It is true that there are a lot of kids that are slower in starting to speak, but if there is a problem, it is best to solve it as soon as possible, because then it will be much harder to handle it.