Sealing generally means that nobody can access the record because it is "sealed." The same holds true for expunged records, except they are normally completely obliterated once they are expunged.
In Texas, there is expungement (which destroys the records), and there is an order of nondisclosure (which seals the records).
An expungement is available to you when the charges are dismissed, or you are found not guilty. An expungement orders state agencies and many private parties to destroy any records of the arrest and court proceedings.
An order of nondisclosure is available to you when you successfully complete a period of deferred adjudication probation. The records will still exist, but they will effectively be sealed from all eyes except for certain members of certain state agencies.
Neither option is available if you have been found guilty, or if you pleaded guilty to straight probation or jail time. An allegation that you were railroaded into a guilty plea by your attorney and that you really didn't do anything and that you've been a good person since then is, unfortunately, not grounds for an expungement or order of nondisclosure.
With regards to both expungement and nondisclosure, there are other factors that affect your eligibility for these solutions, including the crime alleged and your criminal history. If you are looking to expunge or seal your records, look through the records you have of your case and contact a local attorney to determine whether you are eligible for either option.
This answer is based upon the limited information provided in the question and is not intended to create an attorney-client relationship. For more information on your specific legal issue, please contact a local attorney.