Step 10 of 18 of the SMILES tutorial. A heteroatom inside an aromatic ring is written lowercase like everything else in the ring. c1ccncc1 is pyridine: take benzene and turn one aromatic carbon into a lowercase n. The valence model does the rest — this nitrogen ends up with three connections and no hydrogen, exactly as pyridine requires. Try the five-membered heteroaromatics c1ccoc1 (furan) and c1ccsc1 (thiophene).
It opens on c1ccncc1, which you can edit in place: the structure follows every keystroke, and so does the notation when you draw instead.
Convert between chemical structures and SMILES in both directions, search a list of structures by substructure or SMARTS, and learn the notation step by step. Everything runs in your browser — no structure you open ever leaves your machine — so the tool needs JavaScript.