To become law, a bill has to be approved by both chambers - the House and the Senate - and not vetoed by the governor. It must survive a committee hearing in each chamber, and a "floor vote" in each chamber. A bill can continue to change everywhere along the line. Committees produce substitutes and amendments. Bills may also be amended during floor votes. If the second chamber changes the bill that passed out of the first chamber - such as when the House votes on a Senate bill - the differences must be worked out in order for the bill to move forward towards becoming law.
To become law, each bill gets two public committee hearings - first in the chamber in which the bill was filed (House bills in House committees), then in the other chamber (House bills in Senate committees). When a bill is "pending in committee" it has received its public hearing and may be voted out of committee at any time. The bill that gets voted out may be the same as - or different from - the version that was initially filed.
A bill that is changed in committee is called a "Committee Substitute", and it replaces the bill that was initially filed. Most often, the public does not have access to the Committee Substitute until it has passed out of committee and is in queue to be scheduled for a floor vote. The people who testify at hearings may have only seen the version that was initially filed, even though the author announces at the start of the hearing that he is offering a substituted version of the bill. It's not always easy to know if there is a substitute - or to get a copy of it before it's officially posted. Watching the hearing provides clues. On the bill's webpage (on the Lege's website) read what's on the "Actions" tab. Also, under the "Text" tab, look for a "Summary of Committee Action" in the right-hand column.
As the session progresses, the speed picks up, and it becomes increasingly difficult for citizens to monitor changes to a bill in "real time" unless you're pounding the halls of the State Capitol. That's why lobbyists earn their keep ~ they have access.
If you want to know more (and I hope you do), the Lege's website is a treasure trove of information. This will take you to "
How a Bill Becomes Law
" on the Lege's homepage.