Investment is spending that is designed to make money in the future. For example, if a business buys a piece of machinery, that is a form of investment because that machinery is used to generate goods that can be sold for profit. The purchase of an asset that is designed to appreciate in value (e.g. a collectible or a growth stock) also counts as investment.
Whether to count spending as investment or consumption is a principle challenge for government statisticians. Consider the purchase of a home: at first blush, that could count as the purchase of housing services (consumption) or investment (the purchase of an asset that sells housing services in the future). The Bureau of Economic Analysis counts the purchase of a home as an investment (whereupon the occupant “sells housing services to themselves as consumption” in future).