The number of different product lines sold by a company is referred to as width of product mix. The total number of products sold in all lines is referred to as length of product mix. If a line of products is sold with the same brand name, this is referred to as family branding. When you add a new product to a line, it is referred to as a line extension. When you add a line extension that is of better quality than the other products in the line, this is referred to as trading-up or brand leveraging. When you add a line extension that is of lower quality than the other products of the line, this is referred to as trading-down. When you trade-down, you will likely reduce your brand equity. You are gaining short term sales at the expense of long term sales.
Image anchors are highly promoted products within a line that define the image of the whole line. Image anchors are usually from the higher end of the lines' range. When you add a new product within the current range of an incomplete line, this is referred to as line filling.
Price lining in the use of a limited number of prices for all your product offerings. This is a tradition started in the old "five and dime" stores in which everything cost either 5 or 10 cents. Its underlying rationale is that these amounts are seen as suitible price points for a whole range of products by perspective customers. It has the advantage of ease of administering, but the disadvantage of inflexibility, particularly in times of inflation or unstable prices.