To an English-speaking audience, Islam is often advertised as a “monotheistic religion in the tradition of Judaism and Christianity,” and we often, with the best of intentions, add: “The difference is, we only believe in One God.” 
However, this fails to capture the essence of Tawheed, Islam’s concept of monotheism. It is not that there is only one God and that is that. If this were the case, little is there to differentiate us from Christians and Jews, who also conceptually believe in One God (despite different theological formulations). What makes us different is that we believe in One God and, furthermore, we believe that only Allah is to be worshipped.
The core of Islam is wrapped in the message of ‘Laa ilaaha illAllah’: There is no god worthy of worship except Allah. This means, in other words, that we turn away not only from idols of wood and stone, but also the idols of ideology. Today, humanity, spurred by Western culture, worships many things, but above all, it worships itself.
Secularism is the ideology of Western countries (and even some Muslim countries). The reason it works so well is because it is the best, and latest, way to deceive people away from Allah. Rather than urge people to worship forms and shapes, the new Shirk (polytheism) tells people to worship themselves. Everyone is a god!
In Western societies a young woman without a perfect body is an outcast. A young man who cannot party or cannot “get enough girls,” is not a real man - and this is the most interesting example of all.
In Islam, a man’s role is honourable because of his sacrifice and responsibility. A noble and virtuous man is a pious one, who works hard, provides for his family, goes out of his way for his wife and is always faithful to her. Thus, the Muslim character is the responsible and strong one, because the Muslim accepts the Trust from Allah - Islam - and does not shy away from it. 
Allah Tells us in the Qur’an: “And I [Allah] did not create the Jinn and mankind except to worship Me.” [Qur’an: 51:56] The drive to worship is an intrinsic human need. One attempt to crush worship in all forms was communism, and communism - as history attests - failed and continues to fail miserably. Due to the evolution of Western thought and Western society, the drive to worship has been channelled away from Allah and towards the individual. 
However, it does not take long for human beings to realise that we, as individuals, make pathetic idols. At a very young age, we realise we are fallible, and often unsuccessful in many things we wish so sincerely to do. How many kids want to play professional sports, but are never able to?
So, instead, people start to worship ideas. They attribute power to these ideas. They start to believe that governments are all-powerful, or that flags, ethnicities, tribes or languages hold mystical powers. 
In Europe, the popular belief is that every linguistic group deserves a country, because a linguistic group is an immortal entity that has had many members come and go but has, at root, stayed the same. 
But we, as Muslims reject all of this, because we know that it is simply no more than Shirk - partnership in the worship of Allah - which is the unforgivable sin. Why is it unforgivable? The essence of Islam, as stated earlier, is not only that we believe in Allah, but also that we worship Him and make Him the centre of all our efforts. Should we put anything between Allah and ourselves, then we corrupt the purity of our beautiful faith. 
When Prophet Muhammad, 
sallallaahu ‘alaihi wa sallam (may Allah exalt his mention), came to the Arabs of Makkah in 610 CE with a message 
directly from Allah, the Arabs of that time were not atheists. They believed in Allah, they believed He was the most powerful deity and, most interestingly, they believed He could not be 
represented by a physical idol. However, they believed that many idols interceded on their behalf (over 300 lesser gods, in fact!). In other words, the pagans 
believed that there were channels 
between the individual and Allah, and that these barriers needed to be 
worshipped. 
Article source: http://www.islamweb.net/emainpage/