Most important reasons for Islam spread are:
Some think that Islam was spread by wars. This is not true for many reasons. One of these reasons is that the Muslim country of the biggest population is Indonesia while Muslims never invaded Indonesia.
For more information on this refer to related questions below.
they have different reilgions
Persia, India, Europe
It is spreading a lot in Europe, the USA and Australia, but really, it is spreading practically everywhere
Christianity and Islam spread far from where they were founded
the Inquisition was about getting the people of Europe (mostly in Spain and Portugal) to be Catholic again and stop the spread of Judaism and Islam.
Islam spread to libya by other countries
Christianity was dominant and Islamic armies were defeated at the Battle of Tours in 732 C.E. and the Siege of Vienna in 1529 C.E., preventing the expansion of Islam through Europe prior to the 20th century.
Asia - primarily in the south. North Africa A bit into Europe in Spain with the Moors.
A struggle or conflict to spread Islam is a Jihad
Islam never spread by war. Refer to question below.
The Moors invaded Europe to defeat the Christian Visigoths in the Iberian Peninsula. They intended to spread Islam across this area, which is now known as Spain.
The most Islamic Countries are located in Europe,Asia and Africa.They are in this part of the World Because Islam started to spread from Saudi Arabia and slowly Islam expanded to Europe ,Africa Asia(etc)