There are many writing this two words. That is because many do not have a clear understanding of the two words. If you will search its meaning then you can have many results as many have written about it. But you can find also the definition of the individual words and from that, you can try to get the meaning of it. Others wrote that one of the features of the language is that it is widely spoken but the dialect has only a regional setting.
Language may be spoken by the whole nation but within that nation, there are regions or groups that speak their own and that is called dialect. It means that language has a wider coverage but the dialect is small in its scope. Others also just remove the barriers and used the words interchangeably. One definition of a language is that it is one that could be spoken but also could be written. In the side of dialect, it is merely spoken by a group or certain area of people.
But there are many who do not want to define the two and make any differences and similarities statements. Even if they are linguists, they try to avoid having to define one from another and say its differences and similarities or each of their definition. Language and dialect could be also seen to be associated with the politics or it could be in the culture. There could be many things that people could say about this but then what is conclusive and not?