Two different concepts with a lot of overlap.
Should you ever consider buying points?
Alternate Lines
An alternate line takes place when you buy or sell points on a point spread or total. If you want the line to move in your favor (ex. from -6 to -3) you must buy these points.
If you are confident in a game, and you want a greater payout, you would sell the points (ex. From -4 to -7). Alternate lines are most popular in the NFL, but exist for most sports markets.
Here is an example of a payout chart for alternate lines. The point spread for the game is set at 1.5 and is highlighted in green.
Buying Points
Let's say you like the Steelers in the game above, but you are not comfortable with only getting 1.5 points. You would have the option of buying points to give yourself a better chance to win the bet, but it also comes at a cost. You could move the spread to +2.5 (-130), +3.5 (-150) or +4.5 (-175), but the more points you buy, the steeper the price you'd have to pay for that bet.
There are very few instances where it is worth it for you to buy points. What you gain in peace of mind you sacrifice in expected value, as the sportsbooks are typically charging you more the point or points than they are actually worth.
Selling Points
Maybe you really like the 49ers in the game above. If you think they are going to win the game easily, you might feel comfortable selling points to give yourself a bigger payout. Instead of taking the 49ers -1.5 (-110), you may decide to sell 3 points and take them -4.5 (+145). The more points you sell, the bigger your payout, but also the less likely you are to win your bet.
Contrary to buying points, it is often worth it to sell points if you think you have an edge at the current market price.
Game Totals
Alternate lines for game totals also exist, and they work exactly the same as point spreads. Here is an example of alternate line options for an NBA game:
Are Alternate Lines Available in Other Sports?
Yes, alternate lines are available in all of the major sports, and many others as well. From baseball to soccer to even golf, alternate lines are a popular bet type for many sports.
When Should I Use Alternate Lines?
Generally speaking, it is rarely a good idea to buy points. Sportsbooks price these lines at a number where they will turn a profit in the long run. Some bettors will often use alternate lines to avoid "losing by the hook". For example, buying half a point from -3.5 to -3 in the event that their team only wins by a field goal is common practice amongst recreational football bettors, even though this hurts their expected value in the long run.
Price Shopping is Your Friend
If you are absolutely determined to buy points or use alternate lines you should definitely be price shopping. There is no cost to you, and you can save yourself some money in the long run.
'Sportsbook A' may offer the Pacers’ alternate spread at +6 (-155), while 'Sportsbook B' may offer the Pacers’ alternate spread at +6 (-165). You will definitely be able to find a variance in prices being offered by the major sportsbooks, so take the time to shop and increase your chances of winning over time.