projectile motion is all to do with objects being thrown into air. you have to realise that when objects are ''projected'' forward, it's motion is split into two components, the 'vertical' and the 'horizontal'. you MUST consider each motion separately and do calculations using the four basic equations of motion. that's all it is really. everything will be clear to you once you do calculations and understand a bit more..
an example of projectile motion could be : a javelin throw, a cannon ball shoot, throwing a ball far from where you are etc...
