Fractions represent equal parts of a whole. In 1st grade, the focus is on halves and quarters through partitioning concrete shapes and objects, building intuitive understanding before formal notation.
You already know that when you share something with one friend so that you each get the same amount, each person gets a half. Fractions are the math words we use to name those equal parts. The most important idea to understand first is that fractions only work when the parts are equal — the same size. If you break a cookie into two pieces but one piece is much bigger, you do not have halves. You just have two unequal pieces.
When something is split into 2 equal parts, each part is called one-half. We can write that as 1/2. When something is split into 4 equal parts — like a pizza cut into 4 slices — each part is called one-quarter, or one-fourth. We can write that as 1/4. The bottom number tells you how many equal parts the whole was divided into, and the top number tells you how many parts you are talking about.
The best way to understand fractions is to use real things you can see and touch. Fold a piece of paper in half — both sides should match exactly when you fold it. Cut a shape into four equal pieces and put them back together to make the whole shape again. When you see that 4 quarters make one whole, or that 2 halves make one whole, fractions start to make sense as a way of describing real, equal pieces of real things.