Definition

Volume is the measurement of how much space the object or the substance takes up 

Measuring solids through Volume 

To measure volume we need to multiply the width , length and height , now imagine we have a cube , the height is 3.2 cm , the width is 3.2 cm and the length is also 3.2 cm , to get the volume of the object we need to multiply W , L , H , which is 3.2 into 3.2 into 3.2 = 10.24 into 3.2 = 32.768 , thus 32.768 cm cube  is the volume of the cube. 

Measuring liquid through volume

To measure liquids volume we need an equipment called Graduated cylinder , all the graduated cylinder measurements are in millimeters , here is how it looks like 

Now if we pour the amount of water in the glass to the cylinder we may get to notice something , we could observe a meniscus , which is basically that the water will curve in the bottom , 

Measuring irregular solid 

So now let's say we want to know the volume of a stone , we need a cylinder and we should pour a amount of water in it and after that when we put the irregular object , the water level increases cause the volume of the object takes up the outer space , the volume of the solid is actually equal to increase of the water level thus that is how we measure an irregular figures volume