Intangibles are valuable things you cannot touch, such as patents, trademarks, acquired technology, customer lists, and licenses. The accounting quirk to know is that they mostly appear on the balance sheet only when bought. A brand built from scratch rarely shows up no matter how valuable it becomes, which is why companies whose real assets are brands and know-how look expensive on price-to-book (P/B).
Most intangibles are amortized, meaning their cost is spread as an expense over the years they are expected to be useful, exactly as depreciation does for machines.