Islam in general refers to the religion which God Almighty sent His Prophets to teach mankind: The worship of the One God alone (pure Monotheism) while submitting to God's will in gratitude for being given life and innumerable blessings.
According to Islamic belief, the Prophet Muhammad was the last Messenger of God. He, like all of God's prophets and messengers - such as Noah, Abraham, Moses and Jesus -- was only a human being. Christians came to the mistaken assumption that Muslims worship Muhammad by formulating an incorrect analogy - they worship Jesus so they assumed Muslims worship Muhammad. This is one of the reasons that they called Muslims by the incorrect name "Mohammedans" for so many years! Muhammad, like Jesus, never claimed divine status. He called people to worship only Almighty God, and he continually emphasized his humanity so that people would not fall into the same errors as Christians did in regards to Jesus. In order to prevent his deification, the Prophet Muhammad always said to refer to him as "the Messenger of God and His servant". Muhammad was chosen to be God's final messenger --- to communicate the message not only in words but to be a living example of the message. Muslims love and respect him because he was of the highest moral character and he brought the Truth from God - which is the Pure Monotheism of Islam.
Even when Islam was in its very early stages, God revealed that Muhammad "was sent as a mercy to all of mankind" - thus informing us that the message of Islam would become very widespread. Muslims strive to follow the great example of Muhammad, peace be upon him, but they do not worship him in any way. Additionally, Islam teaches Muslims to respect all of God's prophets and messengers - but respecting and loving them does not mean worshipping them. All true Muslims realize that all worship and prayer must be directed to Almighty God alone. Suffice it to say that worshipping Muhammad --- or anyone else --- along with Almighty God is considered to be the worst sin in Islam. Even if a person claims to be Muslim, but they worship and pray to other than Almighty God, this cancels and nullifies their Islam. The Declaration of Faith of Islam makes it clear that Muslims are taught only to worship God. This declaration is as follows: "There is nothing divine or worthy of being worshipped except for Almighty God, and Muhammad is the Messenger and Servant of God".