You will be eligible for unemployment benefits only if you are unemployed through no fault of your own. If you lose your job for economic reasons (for example, because your company can't meet payroll, has decided to close a plant, or has cut back on staffing), you will meet this eligibility requirement.
If you are fired, however, your eligibility will depend on why you lost your job. In most states, if you were fired because you fell short of expectations, failed to meet performance standards, or simply were not a good fit, you will still be eligible for benefits. However, if you were fired for serious misconduct -- as your state defines it -- you can't collect benefits. Some states are more generous than others in this regard, but every state will disqualify someone who was fired for stealing from the employer, committing a crime related to the job, or otherwise acting intentionally against the employer's interests.