Intention (Neeyat)

Everything in Islam is based on intention (Neeyat), which is clearly stated before any act. Marriage, prayers, any act. 

Even if you are fasting for Ramzan, everyday when you wake up for suhoor, and you finish your morsel, you have to state your intent to fast for the coming day. It is in the form of a one line prayer for uniformity. Or at least say in your mind. If you are fasting and never say your neeyat and deep in your heart your intention is to lose weight, then your fasting is not for God. No one except you and God will know that.

Even when we offer our salaat (aka namaaz), we begin with the intention (Neeyat) - 'neeyat karta/ karti hoon main teen rakaat namaaz Farz (depends on type of prayer) waqt Maghrib (depends on time of prayer) waaste Allah Taala ke muh mera kaaba shareef ki taraf. Allahu Akbar'. Of course you can say the neeyat in any language.

For those who don't know Urdu or Hindi, the above means 'I intend to offer 3 parts of obligatory prayer of time maghrib for God's sake while I face the kaaba shareef. God is Great'. Every Muslim in the world faces the Kaaba while praying wherever he/she is located. We have a compass with us to know the direction. There are even special kaaba indicator compasses, which show you location of kabaa from where you are located. 

Rakaat means parts of prayer complete with bowing down on your knees and head touching ground (called 'Sajda'). The types are farz, sunnat, nifil, waajib. All acts of Islam are divided into category. Some are obligatory (farz), some non obligatory but preferable (mostly acts of sunnah). Actually all laws are of 4 types. Will not go into those details in this topic. Times of prayer are Fajr (before sunrise), Zohar (when the sun is overhead), Asar (the time between the sun going down -late afternoon/evening), Maghrib (just a few minutes prior to sunset), Eesha (to be offered at night).