What does the term 'Classical' means?

Classical antiquity (also the classical era, classical period or classical age) is a broad term for a long period of cultural history centered on the Mditerranean Sea, comprising the civilizations of ancient Greece and ancient Rome, collectively known as the Greco-Roman world. It is the period in which Greek and Roman society flourished and performed great influence throughout Europe, North Africa and Southwestern Asia.

When can we set the 'Classical period'?

Conventionally, it is taken to begin with the earliest-recorded Epic Greek poetry of Homer (8th–7th century BC), and continues through the emergence of Christianity and the decline of the Roman Empire (5th century AD). It ends with the dissolution of classical culture at the close of Late Antiquity (300–600), blending into the Early Middle Ages (600–1000).

Which are the main characteristics and influence of this Classical World?

The culture of the ancient Greeks, together with some influences from the ancient Near East, was the basis of art, philosophy, society, and educational ideals, until the Roman imperial period. The Romans preserved, imitated and spread over Europe these ideals until they were able to competitively rival the Greek culture, as the Latin language became widespread and the classical world became bilingual, Greek and Latiin. 
This Greco-Roman cultural foundation has been immensely influential on the language, politics, educational systems, philosophy, science, art, and architecture of the modern world: From the surviving fragments of classical antiquity, a revival movement was gradually formed from the 14th century onwards which came to be known later in Europe as the Renaissance, and again resurgent during various neo-classical revivals in the 18th and 19th centuries.