As the word itself means to compete. When living organism in same species or different species compete for supplies such as food, territory, habitat, power and mating partners it is called as Competition.
It is a type of interaction that occurs within organism in the environment. As the number of organism exceeds than the environment can take care, thus for the survival they need to fight against each other for limited assets.
There are two types of Competition; Intraspecific and Interspecific. In Intraspecific competition, organism of the same species are rivals of each other and is called as Intra-specific.
Example is when the plants of same species are in close proximity for each other, they will fight for obtaining nutrients from the soil, water and sunlight and thus to survive they will adapt themselves in ways such as distorting, increasing in length and evolving with huge roots are some of the example.
The fight which occurs between different organism of different species can be termed as Interspecific competition. An example is, in plants where in the rice field, weeds are also grown.
In animals, the fight could be because of food such as between leopards and lion. Other types of competition are exploitation ad interference competition.