An important part of an attorney's job is to protect the clients' rights during a trial. This includes making sure that the only evidence presented during the trial is evidence that is proper, relevant, and allowed by law. So if evidence is submitted that the attorney feels is improper, or if the attorney feels that the other side is asking questions that are unlawful, the attorney will call out "Objection!"
By doing this, the attorney is asking the judge to rule on whether the law allows that particular piece of evidence or statement or question to be admitted. If the judge thinks it should be admitted, the judge will say, "Objection overruled." If the judge agrees that the evidence in question is improper, the judge will say, "Objection sustained."
How often an attorney raises objections during the trial shouldn't bias you against that attorney's case.