The "Securities and Exchange Commission" or the "SEC" is the federal agency that regulates the offer and sales of securities. The SEC also enforces various securities laws, including insider trading laws and laws relating to proxies.
The term "intraday" means "within the day." The term is often used when stating the high and low prices of a security during a trading day. For example, financial publications will often state that a stock hit a new intraday high, meaning that during the trading day, the stock price reached an all-time high price but went back down to a lower price by the end of the day.