Italian is not a diffucult language, but it is a very precise language, so initially you will have to pay more attention to what you are really saying.
The noun is an extremely important part of the speach. Every noun is either masculine or feminine. Even objects and abstract words such as 'thought' or 'idea' have a gender. In a sentence, adjectives, articles, and sometimes verbs, will have to agree in number and in gender with the noun they modify. That means that your choice of article, adjective and sometimes verb ending, will be guided by the noun. If the noun you are using in your sentence is masculine singular, then all other variable elements above mentioned, will have masculine singular endings.
Eg:
Il ragazzo è simpatico. (The boy is nice)
La ragazza è simpatica. (The girl is nice)
La casa è bella. (The house is beautiful)
Il quadro è bello. (The painting is beautiful)
