Let's Talk- Investing and Power Up

When you convert STEEM to SP, you are not exchanging one currency for another. What you're truly doing is accumulating STEEM over a long period of time. (This is referred to as staking.) You are effectively storing your STEEM in a vault. STEEM is what SP stands for.
You will require SP if you wish to earn money. When you have SP, you gain four things:

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1.You can use your daily allotment of votes to judge content after you have SP. You will be awarded in SP, STEEM, and SBD for doing so. You can also sell your votes to someone who needs them. In addition, if you have SP in your account, you will receive interest. It's not a great sum of money, but it's a nice bonus.
2.A new free account comes with a little quantity of SP and vote delegation. Steemit Inc is just giving you some votes and bandwidth to use.
To create bandwidth, the SP is not used. Instead, you are compensated for staking your STEEM in your account by receiving bandwidth.

3.By storing your STEEM in SP, you gain the ability to vote on who will keep the block chain alive. Your vote carries more weight the more SP you have. If the witness isn't doing a good job recording your data (comments, votes, and transactions) to the block chain, you can vote for someone who is.
4.Others will assume you are merely using Steemit for educational or amusement purposes because of the free account preloaded with SP and no investment from the account owner. That is totally appropriate, but people are less likely to vote if they believe you are only here to read articles.
https://steemit.com/hive-172186/@abdulrazak1/achievement-1-introduction-post-by-abdulrazak1