What is the Meaning & Definition of territorial sea

A territorial sea is the concept that is used to designate that part of the ocean, located adjacent to the coast and extending for 12 nautical miles, which is to say 22.2 km2 and over which a State has absolute sovereignty, as well as with regard to the waters that are inside its territory.
Note, that the main reason and argument when it comes to recognize the sovereignty of the State concerned on the bordering sea lies in that control is essential to ensure their security and defence of their interests.
Anyway, there are some limitations to that State power over the territorial sea and it has to do with the permission that was granted to vessels of other States, as and insofar as possible, the same, does not involve any kind of insult that violates the security of the nation. Such permission is formally known as innocent passage and is seated in the United Nations Convention on the law of the sea; so that in the case of a fast pace and without any extended stops will be allowed vessels of all States navigation by the territorial sea that corresponds.
Another important consideration you need to know about these seas is in the event that the coasts of two States are adjacent or are located face to face, none of the two Nations shall be entitled to extend his domain over the adjacent sea above a line mean it has been equally spaced points with respect to the points nearest to the baselines that is from which is measured the width of the territorial sea of each of the countries, except that a bilateral agreement has been reached.