I'm going to zoom way out for this, so beg your pardon if some of this is known to you.
Everything in the world is made up of atoms. An atom is a single particle of an element, like iron, carbon, sulfur, hydrogen, oxygen, or nitrogen.
Alone, they can't really do much. But when you combine them and hook them together, they form molecules which are infinitely varied. Bonds are what holds the atoms together.
All atoms have three subatomic particles: protons, neutrons, and electrons. The protons and neutrons stay in the nucleus, and give the atom its identity (what defines an element is the number of protons (not neutrons) in its nucleus. Carbon has 6, oxygen has 8, hydrogen just has one, etc). But the electrons? That's where the action is. Electrons sort of exist in a cloud around the nucleus. They are negatively charged, while the protons are positively charged, so they stay associated together. Bonds are when electrons are shared between atoms and hook them together, like linking arms or holding hands. A bunch of atoms connected together form a molecule.
Some bonds - well, most bonds in organic compounds (clarification: in the chemical sense, "organic" only means "molecule that contains carbon" and nothing more) - are what's called covalent bonds, where the atoms share their electrons so they both have their preferred number (that is...another topic). Some bonds are ionic, which is when there's a straight-up handoff of one electron to another. Those are mostly found in salts, like table salt - sodium chloride, NaCl.
But bonds are how the atoms in a molecule stay together.
Like, here's one that's near and dear to our hearts. This is caffeine:
Every corner or end group that is NOT labeled, is a carbon atom. Anything not carbon has to be labeled. This is the common notation, but here is what caffeine looks like as a 3D model:
The black balls are carbon, the nitrogens are blue, the oxygens red, and the white ones are hydrogen atoms. Note that we don't draw the hydrogens at all in the shorthand notation. They're assumed to be there. And we always know how many are there because carbon always makes four bonds, so any bond that is NOT taken up by a bond to another atom, is taken up by hydrogen.
You'll notice that some bonds are one line, and some bonds are a double line. Those are single and double bonds. Which is a topic I probably don't want to wade into here. It has to do with how many electrons the atom has in its outermost layer (the only one that counts).
Hope this helps! Keep asking!
